Different types of collapsible hoppers for conveyors have been proposed. These are meant to collapse when pushed downwardly. This may happen, for example, when the end of a dump truck box is lowered onto the hopper while dumping material into the hopper.
One common collapsible hopper is made of a resilient plastic material. As a truck box presses down on such a hopper, the material yields and deforms elastically. After repeated deformations however, the material takes a set in the collapsed configuration and is no longer useful for its intended purpose.
Other proposals include a flaccid hopper with a resilient frame around its upper periphery and a long compression spring and curved rod system for supporting the frame above the auger inlet. This is a complex system employing multiple sliding and pivoting joints that may be subject to binding.